Jeff wrote:
KLC Lewis wrote:
Never argue bouyancy with Roger Long. ;-)

Why? I think Roger is making a big deal of a very fine distinction. Its
true that an object that is said to be "buoyant" does not generate a
force by itself, the force really comes from water pressure which in
turn is caused by gravity. But, the force is real and buoyancy is
simply a convenient way to aggregate the net pressure on an object. If
there were no force (regardless of what we call it) holding up a ship,
it would sink.

There are, of course, imaginary forces, such as Coriolis which appears
in non-inertial reference frames, but that is a different thing.

Budding naval architects should teach themselves the rudiments of
dimensional analysis... and then they won't make appalling cockups in
their use of incompatible units.

Goofball_star_dot_etal wrote:
Jeff wrote:
KLC Lewis wrote:
Never argue bouyancy with Roger Long. ;-)

Why? I think Roger is making a big deal of a very fine distinction.
Its true that an object that is said to be "buoyant" does not generate
a force by itself, the force really comes from water pressure which in
turn is caused by gravity. But, the force is real and buoyancy is
simply a convenient way to aggregate the net pressure on an object.
If there were no force (regardless of what we call it) holding up a
ship, it would sink.

There are, of course, imaginary forces, such as Coriolis which appears
in non-inertial reference frames, but that is a different thing.

Budding naval architects should teach themselves the rudiments of
dimensional analysis... and then they won't make appalling cockups in
their use of incompatible units.
So who do you think is making an appalling cockup? And in which context?

Jeff wrote:
Goofball_star_dot_etal wrote:
Jeff wrote:
KLC Lewis wrote:
Never argue bouyancy with Roger Long. ;-)

Why? I think Roger is making a big deal of a very fine distinction.
Its true that an object that is said to be "buoyant" does not
generate a force by itself, the force really comes from water
pressure which in turn is caused by gravity. But, the force is real
and buoyancy is simply a convenient way to aggregate the net pressure
on an object. If there were no force (regardless of what we call it)
holding up a ship, it would sink.

There are, of course, imaginary forces, such as Coriolis which
appears in non-inertial reference frames, but that is a different thing.

Budding naval architects should teach themselves the rudiments of
dimensional analysis... and then they won't make appalling cockups in
their use of incompatible units.
So who do you think is making an appalling cockup? And in which context?

There are numerous examples of equating inconsistant units. Here is one
example of gobeldygook:

"Note the net downwards displacement of the air. The essence of all
Newtonian physics is the symmetry of energy conservation (the equal and
opposite reaction business). The work done by accelerating the mass of
air downwards is exactly equal to the work required to keep the aircraft
aloft. The work required to shift it from left to right in the
animations is an important aspect of the drag that the engine must
overcome."

http://www.rogerlongboats.com/Circulation.htm

On Sep 29, 7:32*am, Goofball_star_dot_etal
wrote:

There are numerous examples of equating inconsistant units. Here is one
example of gobeldygook:

The reaction to these presentations on the web is always the same.
The professionals, especially teachers, like them and they gather all
sorts of nit picks from others. That particular bit of gobeldygook
came from an article published in a leading aviation Emagazine and,
last I heard, was being used as an introduction to the subject in at
least one college course.

These are not intended to be physics texts. There are plenty of
those. The intent is to provide a plain language viceral
understanding of the basic principles. Units and terms most
recognizable to the reader with little prior knowledge are preferable
in a quick and light treatment.

Why this kind of thing worthwhile? I've had a whole career (I'm
hardly "budding") to watch people with naval architectural degrees and
complete understanding of the math and unit consistency come to
really bone headed conclusions that have greatly hampered the
commercial and educational sail industries because they didn't start
with a gut understanding of the physics and let numbers and anal
attention to unit consistency lead them to absurd conclusions. If
they had first understood the subject on this kind of level, they
might have made better use of the mathematical tools. Most college
courses and texts start right off with the math.

These articles are just starting points and not intended to be much
above the level of Sunday newpaper supplement stuff. Professionals
tend to see them for what they are and their limited value and net
posters as opportunities to show how smart they are. Happy to have
provided the opportunity.

--
Roger Long

On Sep 29, 10:02*am, Roger Long wrote:
On Sep 29, 7:32*am, Goofball_star_dot_etal
wrote:

There are numerous examples of equating inconsistant units. Here is one
example of gobeldygook:

The reaction to these presentations on the web is always the same.
The professionals, especially teachers, like them and they gather all
sorts of nit picks from others. *That particular bit of gobeldygook
came from an article published in a leading aviation Emagazine and,
last I heard, was being used as an introduction to the subject in at
least one college course.

These are not intended to be physics texts. *There are plenty of
those. *The intent is to provide a plain language viceral
understanding of the basic principles. *Units and terms most
recognizable to the reader with little prior knowledge are preferable
in a quick and light treatment.

Why this kind of thing worthwhile? *I've had a whole career (I'm
hardly "budding") to watch people with naval architectural degrees and
complete understanding of the math and unit consistency *come to
really bone headed conclusions that have greatly hampered the
commercial and educational sail industries because they didn't start
with a gut understanding of the physics and let numbers and anal
attention to unit consistency lead them to absurd conclusions. *If
they had first understood the subject on this kind of level, they
might have made better use of the mathematical tools. *Most college
courses and texts start right off with the math.

These articles are just starting points and not intended to be much
above the level of Sunday newpaper supplement stuff. *Professionals
tend to see them for what they are and their limited value and net
posters as opportunities to show how smart they are. *Happy to have
provided the opportunity.

--
Roger Long

Roger:

Generally pretty good if you take out the part about requiring energy
to float. I'll re-read it sometime today.

Frogwatch (former college Physics teacher who has forgotten more'n he
ever learned)

Frogwatch wrote:

These articles are just starting points and not intended to be much
above the level of Sunday newpaper supplement stuff. Professionals
tend to see them for what they are and their limited value and net
posters as opportunities to show how smart they are. Happy to have
provided the opportunity.

--
Roger Long

Roger:

Generally pretty good if you take out the part about requiring energy
to float. I'll re-read it sometime today.

Frogwatch (former college Physics teacher who has forgotten more'n he
ever learned)


Can we at least agree that the floating boat actually does raise the water level?

"cavelamb" wrote in message
m...

Can we at least agree that the floating boat actually does raise the water
level?

Absolutely. To the same extent that lighting a match increases global
warming. ;-)
--
KLC Lewis

WISCONSIN
Where It's So Cool Outside, Nobody Stays Indoors Napping
www.KLCLewisStudios.com

On Sep 29, 10:13*am, Frogwatch wrote:

Generally pretty good if you take out the part about requiring energy
to float. *I'll re-read it sometime today.


That's not really what it was meant to convey but it's a work in
progress. I'll keep this in mind when I get around to the next round
of revisions.

--
Roger Long

On Tue, 29 Sep 2009 07:02:36 -0700 (PDT), Roger Long
wrote:

On Sep 29, 7:32*am, Goofball_star_dot_etal
wrote:

There are numerous examples of equating inconsistant units. Here is one
example of gobeldygook:

The reaction to these presentations on the web is always the same.
The professionals, especially teachers, like them and they gather all
sorts of nit picks from others. That particular bit of gobeldygook
came from an article published in a leading aviation Emagazine and,
last I heard, was being used as an introduction to the subject in at
least one college course.

These are not intended to be physics texts. There are plenty of
those. The intent is to provide a plain language viceral
understanding of the basic principles. Units and terms most
recognizable to the reader with little prior knowledge are preferable
in a quick and light treatment.

Why this kind of thing worthwhile? I've had a whole career (I'm
hardly "budding") to watch people with naval architectural degrees and
complete understanding of the math and unit consistency come to
really bone headed conclusions that have greatly hampered the
commercial and educational sail industries because they didn't start
with a gut understanding of the physics and let numbers and anal
attention to unit consistency lead them to absurd conclusions. If
they had first understood the subject on this kind of level, they
might have made better use of the mathematical tools. Most college
courses and texts start right off with the math.

These articles are just starting points and not intended to be much
above the level of Sunday newpaper supplement stuff. Professionals
tend to see them for what they are and their limited value and net
posters as opportunities to show how smart they are. Happy to have
provided the opportunity.


Roger, you appear to be re-inventing the wheel. Here is the definition
of buoyancy taken from the Webster dictionary - note the edition date:

2. (Physics) The upward pressure exerted upon a floating body
by a fluid, which is equal to the weight of the body;
hence, also, the weight of a floating body, as measured by
the volume of fluid displaced.
[1913 Webster]

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

On Sep 29, 8:12*pm, Bruce In Bangkok
wrote:

Roger, you appear to be re-inventing the wheel.

I sure hope I am. There isn't supposed to be anything new here.
We're talking about physics after all. It's just supposed to be an
entertaining discussion that makes the subject a bit more accessible
than a physics textbook and emphasizes points that I have encountered
a lot of confusion about, even among people who have advanced
degrees. Read through to the last section. The situation with
sailing vessels arose because USCG naval architects understood all the
math (and how to keep their units consistent but never held in their
mind a gut level understanding of what the number actually represented
and who boats act in the real world.

--
Roger Long